Polyamide resin composition and molded article comprising the same

ABSTRACT

A polyamide resin composition comprising defined amounts of flake graphite, carbon fibers, and polyhydric alcohol. A polyamide resin composition comprising a polyamide resin and, as a property imparting component, at least one member selected from the group consisting of a metal oxide, a nitrogen compound, and a silicon compound, wherein a defined amount of the dicarboxylic acid units of the polyamide resin are oxalic acid. A polyamide resin composition comprising a polyamide resin and a defined amount of metal oxide particles, wherein the metal oxide particles contain those having a particle size of 70 μm or more in an amount of 10 to 50% by mass and those having a particle size of 20 μm or less in an amount of 1 to 50% by mass, based on the total mass of the metal oxide particles.

FIELD OF THE INVENTION

The present invention relates to a polyamide resin composition havingexcellent mechanical properties or electrical insulating properties aswell as excellent thermal conduction properties and a molded articlecomprising the same.

BACKGROUND ART

When graphite is incorporated into a thermoplastic resin, the thermalconduction properties of the resin are improved according to the amountof the graphite incorporated. In the thermoplastic resin havingincorporated thereinto an increased amount of graphite which is notmelted in melt-kneading, the proportion of the thermoplastic resin whichis melted in melt-kneading is reduced, and therefore it is difficult tomaintain the high productivity of the thermoplastic resin in themelt-kneading using a single-screw or twin-screw extruder. Patentdocument 1 discloses that kneading is performed in a state such that thehead portion of an extruder is opened. However, this patent document hasno disclosure of a cooling apparatus, such as a water bath, forefficiently removing heat from the resultant pellets in a flake form,and there is a fear that the pellets stick together, and such kneadingis not preferred from the viewpoint of the molding processability.

The thermoplastic resin having graphite solely incorporated thereintoexhibits unsatisfactory physical properties, such as strength. Patentdocument 2 has a description showing that, by incorporating into athermoplastic resin specific amounts of graphite and carbon fibershaving a thermal conductivity of 100 W/mK or more, the resin is improvedin flexural strength and thermal conduction properties. However, thereis no disclosure of PAN carbon fibers generally used, which have athermal conductivity of about 10 W/mK and which are obtained bycarbonizing polyacrylonitrile fibers.

Polyamide resins, such as polyamide 6 and polyamide 66, have excellentproperties and can be easily melt-molded, and therefore are widely usedas general-purpose engineering plastics. Reference documents 3 and 4disclose that, by incorporating magnesium oxide into the polyamideresin, the resin is improved in thermal conduction properties.

On the other hand, as the increase in density and the miniaturization ofan electronic device progress, the amount of the polyamide resin usedper part for electronic device is reduced, and hence the effect of theproperties of the polyamide resin used on the performance of the partfor electronic device is becoming large. In accordance with this, thereare increasing demands of the improvement of the properties of thepolyamide resin. Especially, there are increasing demands of preventionof the lowering of electrical insulating properties of the polyamideresin, which strongly affects the performance of the part for electronicdevice, under high-temperature and high-humidity conditions (after ahigh-temperature and high-humidity treatment), which are presumed to be,for example, under conditions in the summer in Japan.

When magnesium oxide is incorporated into a thermoplastic resin, thethermal conduction properties of the resin are improved according to theamount of the magnesium oxide incorporated. In the thermoplastic resinhaving incorporated thereinto an increased amount of magnesium oxidewhich is not melted in melt-kneading, the proportion of thethermoplastic resin which is melted in melt-kneading is reduced, andtherefore it is difficult to maintain the high productivity of thethermoplastic resin in the melt-kneading using a single-screw ortwin-screw extruder. As a method of stably filling a resin with anincreased amount of a conductive filler, patent document 1 disclosesthat kneading is performed in a state such that the head portion of anextruder is opened. However, there is no disclosure of a method ofstably filling a resin with an increased amount of a conductive fillerwithout opening the head portion of the extruder.

Further, patent document 5 discloses a method for improving themoldability, appearance, and thermal conduction properties byincorporating magnesium oxide having a specific particle size in aspecific amount. However, in the resultant molded article, the thermalconductivity varies depending on the location of measurement, and thereis no disclosure that a molded article exhibiting a uniform thermalconductivity irrespective of location of measurement is stably obtained.

PRIOR ART REFERENCES Patent Documents

-   Patent document 1: Japanese Unexamined Patent Publication No. Hei    8-1663-   Patent document 2: Japanese Unexamined Patent Publication No.    2003-49081-   Patent document 3: Japanese Unexamined Patent Publication No. Hei    1-213356-   Patent document 4: Japanese Unexamined Patent Publication No. Hei    3-79666-   Patent document 5: Japanese Unexamined Patent Publication No. Hei    3-81366

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide a polyamide resincomposition having excellent mechanical properties or electricalinsulating properties as well as excellent thermal conduction propertiesand a molded article comprising the same.

Another object of the present invention is to provide a polyamide resincomposition which is advantageous not only in that the composition canachieve both high thermal conduction properties and high mechanicalproperties without using carbon fibers having a thermal conductivity of100 W/mK or more, but also in that the polyamide resin composition withexcellent productivity.

Still another object of the present invention is to provide a polyamideresin composition which is prevented from lowering in electricalinsulating properties after a high-temperature and high-humiditytreatment, and which exhibits excellent thermal conduction properties.

A further task of the present invention is to provide a polyamide resincomposition advantageous in that there can be obtained a molded articlewhich can be stably produced by a general kneader without opening thehead portion of the extruder (kneader), and which exhibits uniformthermal conduction properties.

Means to Solve the Problems

The above-mentioned problems are solved by the present invention shownbelow.

1. A polyamide resin composition comprising a polyamide resin (A) and aproperty imparting component, the composition being:

(1) a polyamide resin composition which comprises, relative to 100 partsby volume of the polyamide resin (A), as the property impartingcomponent, 50 to less than 100 parts by volume of flake graphite (B), 5to 40 parts by volume of carbon fibers (C), and 0.1 to 5 parts by volumeof a polyhydric alcohol (D);

(2) a polyamide resin composition which comprises the polyamide resin(A) which is a polyamide resin (A1) comprising dicarboxylic acid units(x) and diamine units (y) as constitutional units, and the propertyimparting component which is at least one member selected from the groupconsisting of a metal oxide (B1), a nitrogen compound (B2), and asilicon compound (B3), wherein the dicarboxylic acid units (x) of thepolyamide resin (A1) are oxalic acid in an amount of 70 mol % or more,based on the total dicarboxylic acid units of the polyamide resin (A1);or

(3) a polyamide resin composition which comprises the polyamide resin(A) and metal oxide particles (BB) as the property imparting component,wherein the metal oxide particles (BB) contain those having a particlesize of 70 μm or more in an amount of 10 to 50% by mass and those havinga particle size of 20 μm or less in an amount of 1 to 50% by mass, basedon the total mass of the metal oxide particles, wherein the metal oxideparticles (BB) are contained in an amount of 70 to 85% by mass, based onthe mass of the polyamide resin composition.

2. The polyamide resin composition according to item 1 above, whichcomprises, relative to 100 parts by volume of the polyamide resin (A),50 to less than 100 parts by volume of the flake graphite (B), 5 to lessthan 40 parts by volume of the carbon fibers (C), and 0.1 to 5 parts byvolume of the polyhydric alcohol (D);

3. The polyamide resin composition according to item 2 above, whereinthe polyhydric alcohol (D) is a polyhydric alcohol having a meltingtemperature of 150 to 280° C.;

4. The polyamide resin composition according to item 2 or 3 above, whichis obtainable by melt-kneading;

5. The polyamide resin composition according to item 1 above, whichcomprises the polyamide resin (A1) comprising dicarboxylic acid units(x) and diamine units (y) as constitutional units, and at least onemember selected from the group consisting of a metal oxide (B1), anitrogen compound (B2), and a silicon compound (B3), wherein thedicarboxylic acid units (x) of the polyamide resin (A1) are oxalic acidin an amount of 70 mol % or more, based on the total dicarboxylic acidunits of the polyamide resin (A1);

6. The polyamide resin composition according to item 5 above, whereinthe metal oxide (B1) is magnesium oxide;

7. The polyamide resin composition according to item 5 or 6 above, whichis for use in an electrical insulating part; and

8. The polyamide resin composition according to item 1 above, whichcomprises the polyamide resin (A) and the metal oxide particles (BB),wherein the metal oxide particles (BB) contain those having a particlesize of 70 μm or more in an amount of 10 to 50% by mass and those havinga particle size of 20 μm or less in an amount of 1 to 50% by mass, basedon the total mass of the metal oxide particles, wherein the metal oxideparticles (BB) are contained in an amount of 70 to 85% by mass, based onthe mass of the polyamide resin composition;

9. The polyamide resin composition according to item 8 above, whichfurther comprises the polyhydric alcohol (D) in an amount of 0.1 to 5%by mass, based on the mass of the polyamide resin composition;

10. The polyamide resin composition according to item 8 or 9 above,wherein the metal oxide particles (BB) are magnesium oxide;

11. A molded article comprising the polyamide resin compositionaccording to any one of items 1 to 10 above.

Effect of the Invention

By the present inventions 1 to 11, there can be provided a polyamideresin composition which is advantageous in that a molded article havingexcellent mechanical properties or electrical insulating properties aswell as excellent thermal conduction properties can be obtained.

By the present inventions 2 to 4 and 11, further, there can be provideda polyamide resin composition which is advantageous in that a moldedarticle having both excellent thermal conduction properties andexcellent mechanical properties can be obtained without using carbonfibers having a thermal conductivity of 100 W/mK or more, and there canbe provided a method which can stably pelletize the polyamide resincomposition by a general twin-screw extruder.

By the present inventions 5 to 7 and 11, further, there can be provideda polyamide resin composition which is advantageous in that a moldedarticle having excellent electrical insulating properties even after ahigh-temperature and high-humidity treatment and having both excellentthermal conduction properties and excellent mechanical properties can beobtained. The polyamide resin composition has especially excellentelectrical insulating properties after a high-temperature andhigh-humidity treatment, and therefore can be preferably used as anelectrical insulating material in an electrical insulating part.

By the present inventions 8 to 11, further, there can be provided apolyamide resin composition which is advantageous in that there can beobtained a molded article which can be stably produced by a generalkneader without opening the head portion of the kneader, and whichexhibits uniform thermal conduction properties.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a view showing locations of measurement of thermalconductivity for evaluating the thermal conduction properties.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is directed to a polyamide resin compositioncomprising polyamide resin (A) and a property imparting component,wherein the composition is:

(1) a polyamide resin composition which comprises, relative to 100 partsby volume of polyamide resin (A), as the property imparting component,50 to less than 100 parts by volume of flake graphite (B), 5 to 40 partsby volume of carbon fibers (C), and 0.1 to 5 parts by volume ofpolyhydric alcohol (D);

(2) a polyamide resin composition which comprises polyamide resin (A)which is polyamide resin (A1) comprising dicarboxylic acid units (x) anddiamine units (y) as constitutional units, and the property impartingcomponent which is at least one member selected from the groupconsisting of metal oxide (B1), nitrogen compound (B2), and siliconcompound (B3), wherein dicarboxylic acid units (x) of polyamide resin(A1) are oxalic acid in an amount of 70 mol % or more, based on thetotal mole of the dicarboxylic acid units of polyamide resin (A1); or

(3) a polyamide resin composition which comprises polyamide resin (A)and metal oxide particles (BB) as the property imparting component,wherein metal oxide particles (BB) contain those having a particle sizeof 70 pin or more in an amount of 10 to 50% by mass and those having aparticle size of 20 μm or less in an amount of 1 to 50% by mass, basedon the total mass of the metal oxide particles, wherein metal oxideparticles (BB) are contained in an amount of 70 to 85% by mass, based onthe mass of the polyamide resin composition.

[Polyamide Resin Composition A]

The present invention can be polyamide resin composition A whichcomprises, relative to 100 parts by volume of polyamide resin (A), 50 toless than 100 parts by volume of flake graphite (B), 5 to 40 parts byvolume of carbon fibers (C), and 0.1 to 5 parts by volume of polyhydricalcohol (D).

The part(s) by volume used in the present invention is determined asfollows. Volumes of polyamide resin (A), flake graphite (B), carbonfibers (C), and polyhydric alcohol (D) are individually determined fromthe respective masses and the respective specific gravities underatmospheric pressure (1 atm.) at 25° C., and, relative to 100 parts byvolume of polyamide resin (A), part(s) by volume of each of flakegraphite (B), carbon fibers (C), and polyhydric alcohol (D) isdetermined.

[Polyamide Resin (A)]

With respect to polyamide resin (A) used in polyamide resin compositionA of the present invention, there is no particular limitation as long asit is a polyamide resin obtained by polymerization or copolymerizationby a known method, such as melt polymerization, solution polymerization,or solid-phase polymerization.

Examples of polyamide resins (A) include polycaprolactam (polyamide 6),polyundecanelactam (polyamide 11), polydodecanelactam (polyamide 12),polyethyleneadipamide (polyamide 26), polytetramethyleneadipamide(polyamide 46), polyhexamethyleneadipamide (polyamide 66),polyhexamethyleneazelamide (polyamide 69), polyhexamethylenesebacamide(polyamide 610), polyhexamethyleneundecamide (polyamide 611),polyhexamethylenedodecamide (polyamide 612),polyhexamethyleneterephthalamide (polyamide 6T),polyhexamethyleneisophthalamide (polyamide 6I),polyhexamethylenehexahydroterephthalamide (polyamide 6T(H)),polynonamethyleneadipamide (polyamide 96), polynonamethyleneazelamide(polyamide 99), polynonamethylenesebacamide (polyamide 910),polynonamethylenedodecamide (polyamide 912),polynonamethyleneterephthalamide (polyamide 9T),polytrimethylhexamethyleneterephthalamide (polyamide TMHT),polynonamethylenehexahydroterephthalamide (polyamide 9T(H)),polynonamethylenenaphthalamide (polyamide 9N),polydecamethyleneadipamide (polyamide 106), polydecamethyleneazelamide(polyamide 109), polydecamethylenedecamide (polyamide 1010),polydecamethylenedodecamide (polyamide 1012),polydecamethyleneterephthalamide (polyamide 10T),polydecamethylenehexahydroterephthalamide (polyamide 10T(H)),polydecamethylenenaphthalamide (polyamide 10N),polydodecamethyleneadipamide (polyamide 126),polydodecamethyleneazelamide (polyamide 129),polydodecamethylenesebacamide (polyamide 1210),polydodecamethylenedodecamide (polyamide 1212),polydodecamethyleneterephthalamide (polyamide 12T),polydodecamethylenehexahydroterephthalamide (polyamide 12T(H)),polydodecamethylenenaphthalamide (polyamide 12N),polymetaxylyleneadipamide (polyamide MXD6), polymetaxylylenesuberamide(polyamide MXD8), polymetaxylyleneazelamide (polyamide MXD9),polymetaxylylenesebacamide (polyamide MXD10), polymetaxylylenedodecamide(polyamide MXD12), polymetaxylyleneterephthalamide (polyamide MXDT),polymetaxylyleneisophthalamide (polyamide MXDI),polymetaxylylenenaphthalamide (polyamide MXDN),polybis(4-aminocyclohexyl)methanedodecamide (polyamide PACM12),polybis(4-aminocyclohexyl)methaneterephthalamide (polyamide PACMT),polybis(4-aminocyclohexyl)methaneisophthalamide (polyamide PACMI),polybis(3-methyl-4-aminocyclohexyl)methanedodecamide (polyamidedimethylPACM12), polyisophoroneadipamide (polyamide IPD6),polyisophoroneterephthalamide (polyamide IPDT), and polyamide copolymersusing a raw material monomer for the above resins. These can be usedindividually or in combination. Of these, preferred are polyamide 6,polyamide 12, polyamide 66, polyamide 6/66 copolymer (which indicates acopolymer of polyamide 6 and polyamide 66; hereinafter, a copolymer isindicated according to the same manner), polyamide 6/69 copolymer,polyamide 6/610 copolymer, polyamide 6/611 copolymer, polyamide 6/612copolymer, polyamide 6/12 copolymer, polyamide 6/66/12 copolymer,polyamide 6/IPD6 copolymer, and polyamide MXD6, more preferred arepolyamide 6, polyamide 12, polyamide 66, polyamide 6/66 copolymer,polyamide 6/12 copolymer, polyamide 6/IPD6 copolymer, and polyamide6/66/12 copolymer, and further preferred are polyamide 6, polyamide 66,and polyamide 6/66 copolymer, and, from the viewpoint of achievingexcellent molding processability, polyamide 6 is especially preferred.

With respect to the type of the terminal group, the concentration, andthe molecular weight distribution of polyamide resin (A) in the presentinvention, there is no particular limitation, and, for controlling themolecular weight and stabilizing the melted resin during the molding, asa molecular weight modifier, a monocarboxylic acid, such as acetic acidor stearic acid, a diamine, such as metaxylylenediamine orisophoronediamine, a monoamine, and a dicarboxylic acid can be usedindividually or in appropriate combination.

Polyamide resin (A) can be produced by means of an apparatus forproducing polyamide, e.g., a batch reactor, a single-reactor ormulti-reactor continuous reaction apparatus, a tubular continuousreaction apparatus, or a kneading reaction extruder, such as asingle-screw extruder or a twin-screw extruder.

Examples of polymerization methods include melt polymerization, solutionpolymerization, and solid-phase polymerization. These polymerizationmethods can be conducted by repeating operations under atmosphericpressure, under a reduced pressure, and under a pressure, and can beused individually or in appropriate combination.

The relative viscosity of polyamide resin (A), as measured in accordancewith JIS K-6920 under conditions such that the concentration of thepolyamide in 96% by mass sulfuric acid is 1% by mass and the temperatureis 25° C., is preferably 1.0 to 6.0, especially preferably 1.5 to 5.0,more preferably 1.7 to 4.5. When the relative viscosity of the polyamideresin is less than the above-mentioned value, the resultant moldedarticle may be reduced in mechanical properties. On the other hand, whenthe relative viscosity of the polyamide resin exceeds theabove-mentioned value, the viscosity of the melted composition may beincreased, making it difficult to mold the composition into a moldedarticle. Further, from the viewpoint of achieving excellent productivityof the polyamide resin composition of the present invention andexcellent moldability of the molded article, the relative viscosity ofpolyamide resin (A) is further preferably 2.0 to 3.0.

With respect to the water extraction of polyamide resin (A) as measuredin accordance with the method described in JIS K-6920 for measuring alow molecular-weight substance content, there is no particularlimitation, but there is a possibility that gas and others generatedduring the molding cause environmental problems, or adhere to theproduction facilities to lower the productivity or adhere to productpellets to cause the appearance to be poor, and therefore the waterextraction of polyamide resin (A) is preferably 5% by mass or less.

The form of particles of polyamide resin (A) is preferably a powderyform having an average particle size of 1 mm or less from the viewpointof uniformly mixing flake graphite (B) and other additives. With respectto the method for obtaining a powdery form, there is no particularlimitation, but, from the viewpoint of achieving excellent productivityof the powder, freeze-grinding is preferred.

In polyamide resin (A) in the present invention, various additives andmodifiers generally incorporated to a resin can be added in such anamount that the properties of the resultant molded article are notsacrificed. For example, a heat stabilizer, an ultraviolet lightabsorber, a light stabilizer, an antioxidant, an antistatic agent, alubricant, an anti-blocking agent, a filler, a tackifier, a sealingproperty improving agent, an anti-fogging agent, a crystal nucleatingagent, a release agent, a plasticizer, a crosslinking agent, a foamingagent, a coloring agent (e.g., a pigment or a dye), and the like can beadded. With respect to the method for adding the above additive, thereis no particular limitation, and various types of methods conventionallyknown can be employed. For example, the additive can be added by a dryblending method, or by a melt kneading method, together with anothercomponent incorporated if necessary. Melt-kneading can be made using akneader, such as a single-screw extruder, a twin-screw extruder, akneader, or a Banbury mixer.

Polyamide resin composition A of the present invention contains flakegraphite (B), carbon fibers (C), and polyhydric alcohol (D).

[Flake Graphite (B)]

Flake graphite (B) used in polyamide resin composition A of the presentinvention is obtained by refining natural graphite and processing theresultant graphite having an increased purity into a flake form. Withrespect to the average particle size of the flake graphite, there is noparticular limitation, but the average particle size is generally 1 to100 μm, preferably 5 to 80 μm. When the average particle size of theflake graphite is less than 1 μm, the flake graphite has an increasedbulk specific gravity, that is, the volume of air per unit volume isincreased, and therefore the weight of the graphite which can beintroduced to a hopper during the melt-kneading is reduced, and thus thenumber of the operations of introducing the graphite to the hopper isinevitably increased, and this is not preferred from the viewpoint ofproduction efficiency. On the other hand, when the average particle sizeof the flake graphite is 100 μm or more, mechanical strength, such as animpact strength, tends to lower.

With respect to the aspect ratio (average particle size/averagethickness) of flake graphite (B) used in polyamide resin composition Aof the present invention, there is no particular limitation, but, fromthe viewpoint of achieving excellent mechanical properties includingimpact strength and excellent thermal conduction properties, the aspectratio is advantageously 30 to 300 on average, preferably 30 to 200 onaverage, more preferably 30 to 150 on average.

From the viewpoint of achieving excellent productivity and excellentthermal conduction properties as well as excellent mechanicalproperties, the amount of flake graphite (B) incorporated into polyamideresin composition A of the present invention is, relative to 100 partsby volume of polyamide resin (A), preferably 50 to less than 100 partsby volume, more preferably 60 to 97 parts by volume, further preferably70 to 93 parts by volume, especially preferably more than 80 to 91 partsby volume.

[Carbon Fibers (C)]

Carbon fibers (C) used in polyamide resin composition A of the presentinvention are PAN carbon fibers obtainable by carbonizingpolyacrylonitrile fibers.

With respect to the fiber length of carbon fibers (C), short fibers maybe used according to the use, and continuous fibers having a fiberlength as large as 1,000 mm may be used, and, from the viewpoint ofachieving excellent productivity including feeding properties to atwin-screw extruder, the fiber length of the carbon fibers beforekneaded is preferably 0.1 to 20 mm, more preferably 1 to 15 mm.

With respect to the fiber diameter of carbon fibers (C), there is noparticular limitation. The carbon fibers having a smaller fiber diameterare likely to exhibit a strength in the resin composition or moldedarticle, but the carbon fibers having too small a fiber diameter may befibrillated, for example, when being fed to a kneader, lowering theproduction efficiency in the kneading. From the viewpoint of achievingexcellent productivity in a kneader and excellent mechanical propertiesincluding strength, the fiber diameter is preferably 5 to 15 μm. Amasterbatch preliminarily having carbon fibers contained in a resin at ahigh content or granulated carbon fibers are unlikely to cause thecarbon fibers to be fibrillated during the production of the polyamideresin composition of the present invention, and therefore are preferredwhen using carbon microfibers.

From the viewpoint of achieving excellent productivity and excellentthermal conduction properties as well as excellent mechanicalproperties, the amount of carbon fibers (C) incorporated into polyamideresin composition A of the present invention is, relative to 100 partsby volume of polyamide resin (A), preferably 5 to less than 40 parts byvolume, more preferably 6 to 30 parts by volume, further preferably 8 to20 parts by volume.

[Polyhydric Alcohol (D)]

With respect to the polyhydric alcohol used in polyamide resincomposition A of the present invention, there is no particularlimitation, but a polyhydric alcohol having a melting temperature of 150to 280° C. is preferred. The melting temperature means a temperature atan endothermic peak (melting point) as measured by differential scanningcalorimetry (DSC) used for measuring a melting point and a freezingpoint of a resin. Examples of polyhydric alcohols having a meltingtemperature of 150 to 280° C. include pentaerythritol,dipentaerythritol, and trimethylolethane, and these can be used incombination. From the viewpoint of achieving excellent kneadingproperties and excellent moldability, pentaerythritol and/ordipentaerythritol is preferred.

Further, from the viewpoint of achieving excellent kneading propertiesand excellent moldability, the amount of polyhydric alcohol (D)incorporated into polyamide resin composition A of the present inventionis, relative to 100 parts by volume of the polyamide resin, preferably0.1 to 5 parts by volume, more preferably 0.5 to 3 parts by volume.

In polyamide resin composition A, from the viewpoint of achievingexcellent productivity and excellent thermal conduction properties aswell as excellent mechanical properties, the amount of flake graphite(B) is, relative to 100 parts by volume of polyamide resin (A),preferably 50 to less than 100 parts by volume, more preferably 97 partsby volume or less, further preferably 70 to 93 parts by volume,especially preferably more than 80 to 91 parts by volume. From theviewpoint of achieving excellent productivity and excellent thermalconduction properties as well as excellent mechanical properties, theamount of carbon fibers (C) is, relative to 100 parts by volume ofpolyamide resin (A), preferably 5 to less than 40 parts by volume, morepreferably 6 to 30 parts by volume, more preferably 8 to 20 parts byvolume. From the viewpoint of achieving excellent kneading propertiesand excellent moldability, the amount of polyhydric alcohol (D) is,relative to 100 parts by volume of polyamide resin (A), preferably 0.1to 5 parts by volume, more preferably 0.5 to 3 parts by volume.

With respect to the method for producing polyamide resin composition Aof the present invention, there is no particular limitation as long asthe composition is produced by melt-kneading, and various types ofmethods conventionally known can be employed. For example, the polyamideresin composition can be produced using a kneader, such as asingle-screw extruder, a twin-screw extruder, a kneader, or a Banburymixer. Especially, the polyamide resin composition of the presentinvention can be preferably produced using a single-screw extruder or atwin-screw extruder.

As a method for molding polyamide resin composition A of the presentinvention into a molded article, a molding method, such as injection,extrusion, or pressing, can be employed. The polyamide resin compositioncan be processed by the above molding method into, e.g., a moldedarticle or a sheet.

The molded product using polyamide resin composition A of the presentinvention can be used in various types of molded articles, sheets andfibers in which a molded product of a polyamide resin composition hasconventionally been used, and a wide variety of applications, such asautomobile members, computers and associated devices, optical devicemembers, electric and electronic devices, information and communicationdevices, precision devices, civil engineering and construction products,medical products, and household products. The molded product usingpolyamide resin composition A is especially useful in applications, suchas automobiles and electric and electronic devices.

[Polyamide Resin Composition B]

The present invention can be polyamide resin composition B whichcomprises polyamide resin (A1) comprising dicarboxylic acid units (x)and diamine units (y) as constitutional units, and at least one memberselected from the group consisting of metal oxide (B1), nitrogencompound (B2), and silicon compound (B3), wherein dicarboxylic acidunits (x) of polyamide resin (A1) are oxalic acid in an amount of 70 mol% or more, based on the total mole of dicarboxylic acid units ofpolyamide resin (A1).

[Polyamide Resin (A1)]

In polyamide resin (A1) in polyamide resin composition B of the presentinvention, dicarboxylic acid units (x) are oxalic acid in an amount of70 mol % or more, preferably 80 mol % or more, more preferably 90 mol %or more, further preferably 98 to 100 mol %, based on the total mole ofthe dicarboxylic acid units.

With respect to the oxalic acid source of dicarboxylic acid units (x),an oxalic diester is used, and, with respect to the oxalic diester,there is no particular limitation as long as it has reactivity with anamino group, and examples include oxalic diesters of an aliphaticmonohydric alcohol, such as dimethyl oxalate, diethyl oxalate, di-n-(ori-)propyl oxalate, and di-n-(, i-, or t-)butyl oxalate; oxalic diestersof an alicyclic alcohol, such as dicyclohexyl oxalate; and oxalicdiesters of an aromatic alcohol, such as diphenyl oxalate.

Among the above-mentioned oxalic diesters, preferred are oxalic diestersof an aliphatic monohydric alcohol having more than 3 carbon atoms,oxalic diesters of an alicyclic alcohol, and oxalic diesters of anaromatic alcohol, and, of these, more preferred are dibutyl oxalate anddiphenyl oxalate.

Polyamide resin (A1) can contain other dicarboxylic acid units (x),lactam units, and aminocarboxylic acid units as long as dicarboxylicacid units (x) comprise oxalic acid in an amount of 70 mol % or more,based on the total mole of the dicarboxylic acid units.

Examples of other dicarboxylic acid units include aliphatic dicarboxylicacids, such as malonic acid, dimethyl malonate, succinic acid, glutaricacid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacicacid, undecanedicarboxylic acid, dodecanedicarboxylic acid,tridecanedicarboxylic acid, tetradecanedicarboxylic acid,pentadecanedicarboxylic acid, hexadecanedicarboxylic acid,octadecanedicarboxylic acid, and eicosanedicarboxylic acid; alicyclicdicarboxylic acids, such as 1,3-/1,4-cyclohexanedicarboxylic acid,dicyclohexanemethane-4,4′-dicarboxylic acid, and norbornanedicarboxylicacid; and aromatic dicarboxylic acids, such as isophthalic acid,terephthalic acid, and 1,4-/2,6-/2,7-naphthalenedicarboxylic acid. Thesecan be used individually or in combination.

Examples of lactam units include caprolactam, enantholactam,undecanelactam, dodecanelactam, and α-pyrrolidone. These can be usedindividually or in combination.

Examples of aminocarboxylic acid units include aminocaproic acid andaminododecanoic acid.

In polyamide resin composition B of the present invention, examples ofdiamine units (y) of polyamide resin (A1) include aliphatic diamines,such as 1,2-ethylenediamine, 1,3-trimethylenediamine,1,4-tetramethylenediamine, 1,5-pentamethylenediamine,1,6-hexamethylenediamine(1,6-hexanediamine), 1,7-heptamethylenediamine,1,8-octamethylenediamine, 1,9-nonamethylenediamine,2-methyl-1,8-octanediamine, 1,10-decamethylenediamine,1,11-undecamethylenediamine, 1,12-dodecamethylenediamine,1,13-tridecamethylenediamine, 1,14-tetradecamethylenediamine,1,15-pentadecamethylenediamine, 1,16-hexadecamethylenediamine,1,17-heptadecamethylenediamine, 1,18-octadecamethylenediamine,1,19-nonadecamethylenediamine, 1,20-cicosamethylenediamine,2-/3-methyl-1,5-pentanediamine, 2-methyl-1,8-octanediamine,2,2,4-/2,4,4-trimethylhexamethylenediamine, and5-methyl-1,9-nonanediamine; alicyclic diamines, such as1,3-/1,4-cyclohexanediamine, 1,3-/1,4-cyclohexanedimethylamine,bis(4-aminocyclohexyl)methane, bis(4-aminocyclohexyl)propane,bis(3-methyl-4-aminocyclohexyl)methane,bis(3-methyl-4-aminocyclohexyl)propane,5-amino-2,2,4-trimethyl-1-cyclopentanemethylamine,5-amino-1,3,3-trimethylcyclohexanemethylamine(isophoronediamine),bis(aminopropyl)piperazine, bis(aminoethyl)piperazine,norbornanedimethylamine, and tricyclodecanedimethylamine; and aromaticdiamines, such as p-phenylenediamine, m-phenylenediamine,m-xylylenediamine, p-xylylenediamine, 4,4′-diaminodiphenyl sulfone, and4,4′-diaminodiphenyl ether. Of these, preferred are1,6-hexamethylenediamine(1,6-hexanediamine), 1,9-nonamethylenediamine,2-methyl-1,8-octanediamine, 1,10-decamethylenediamine,1,11-undecamethylenediamine, 1,12-dodecamethylenediamine,m-xylylenediamine, and p-xylylenediamine, more preferred are1,6-hexamethylenediamine(1,6-hexanediamine), 1,9-nonamethylenediamine,2-methyl-1,8-oetanediamine, and m-xylylenediamine, and further preferredare 1,9-nonamethylenediamine and 2-methyl-1,8-octanediamine. These canbe used individually or in combination.

When 1,9-nonamethylenediamine and 2-methyl-1,8-octanediamine are mixed,molar ratio of the 1,9-nonamethylenediamine to2-methyl-1,8-octanediamine is 1:99 to 99:1, preferably 5:95 to 95:5,more preferably 5:95 to 40:60 or 60:40 to 95:5, particularly 5:95 to30:70 or 70:30 to 90:10. By copolymerizing 1,9-nonamethylenediamine and2-methyl-1,8-octanediamine in the above-mentioned specific amounts,there can be obtained polyamide resin (A1) advantageous not only in thatit has a broad width of the temperature at which the resin can bemolded, but also in that it exhibits excellent melt moldability as wellas excellent chemical resistance and excellent resistance to hydrolysis.

In polyamide resin composition B of the present invention, specificexamples of polyamide resins (A1) include polyamide 62, polyamide 82,polyamide 92, polyamide 102, polyamide 122, polyamide 62/92 copolymer,polyamide 62/102 copolymer, polyamide 62/122 copolymer, polyamide 92/102copolymer, and polyamide 92/122 copolymer. These can be usedindividually or in combination. From the viewpoint of achievingexcellent resistance to hydrolysis and excellent molding processability,preferred are polyamide 92, polyamide 122, and polyamide 62/92copolymer, and polyamide 92 is more preferred.

Polyamide resin (A1) in polyamide resin composition B of the presentinvention is a polymer comprising a salt of oxalic acid which is adicarboxylic acid, and a diamine as polymerization units, and thereforeis generally called polyamide. A salt of oxalic acid and a diamine isreferred to as oxamide, and hence a polymer comprising an oxamide aspolymerization units is referred to also as polyoxamide.

Polyamide resin (A1) used in polyamide resin composition B of thepresent invention can be produced using an arbitrary method known as amethod for producing polyamide, for example, a solution polymerizationmethod, an interfacial polymerization method, a melt polymerizationmethod, or a solid-phase polymerization method. Specifically, thepolyamide resin can be obtained by reacting a diamine and an oxalicdiester with each other in a batchwise manner or in a continuous manner,and the operations for the production are preferably conducted in theorder of (i) the former polymerization step and (ii) the latterpolymerization step shown below.

In the former polymerization step (i), after or while purging a reactorwith nitrogen, dicarboxylic acid units (x) and diamine units (y) aremixed with each other. A solvent capable of dissolving therein bothdicarboxylic acid units (x) and diamine units (y) may be used in mixingthem. With respect to the solvent capable of dissolving therein bothdiamine units (y) and an oxalic diester as dicarboxylic acid units (x),there is no particular limitation, but, for example, toluene, xylene,trichlorobenzene, phenol, or trifluoroethanol can be used, and toluenecan be especially preferably used. For example, a toluene solutionhaving a diamine dissolved is heated to 50° C. and then, an oxalicdiester is added to the solution. In this instance, the ratio of thecharged oxalic diester to the charged diamine is 0.8 to 1.5, preferably0.91 to 1.1, further preferably 0.99 to 1.01, in terms of the oxalicdiester/diamine ratio (molar ratio).

The elevation of the temperature in the reactor into which the materialsare charged as mentioned above is started under atmospheric pressurewhile stirring and/or introducing a jet of bubbles using nitrogen, sothat the temperature in the reactor and the pressure in the reactorpreferably finally become 100 to 270° C. and atmospheric pressure,respectively, in this step.

In the latter polycondensation step (ii), for further increasing themolecular weight of the polymerization product formed in the previousstep, the temperature of the polymerization product formed in theprevious step is gradually elevated in the reactor under atmosphericpressure. In the temperature elevation process, the temperature iselevated from the final temperature in the former polycondensation stepfinally to a temperature in the range of 220 to 300° C., preferably 230to 280° C., further preferably 240 to 270° C. The reaction is preferablyconducted for 1 to 8 hours, preferably 2 to 6 hours, including thetemperature elevation time. Further, in the latter polymerization step,if necessary, the polymerization can be conducted under a reducedpressure.

In the production of polyamide resin (A1), as a catalyst, phosphoricacid, phosphorous acid, hypophosphorous acid, or a salt or ester thereofcan be used. Specific examples of catalysts include metal salts, such aspotassium, sodium, magnesium, vanadium, calcium, zinc, cobalt,manganese, tin, tungsten, germanium, titanium, and antimony salts,ammonium salts, ethyl esters, isopropyl esters, butyl esters, hexylesters, isodecyl esters, octadecyl esters, decyl esters, stearyl esters,and phenyl esters.

With respect to the relative viscosity of polyamide resin (A1) inpolyamide resin composition B of the present invention, there is noparticular limitation, but, from the viewpoint of achieving excellentmolding processability and excellent impact properties, the relativeviscosity of a solution having a polyamide resin concentration of 1.0g/dl using 96% by mass sulfuric acid as a solvent as measured at 25° C.is preferably 1.8 to 6.0, more preferably 2.0 to 5.5, further preferably2.5 to 4.5.

In polyamide resin composition B of the present invention, with respectto the melting temperature of polyamide resin (A1), there is noparticular limitation, but the melting temperature is preferably 150 to350° C., and, from the viewpoint of achieving excellent moldingprocessability, the melting temperature of polyamide resin (A1) is morepreferably 200 to 300° C.

With respect to the form of particles of polyamide resin (A1), there isno particular limitation, but, from the viewpoint of uniformly mixingmetal oxide (B1), a powdery form having an average particle size of 1 mmor less is preferred. With respect to the method for obtaining a powderyform, there is no particular limitation, but, from the viewpoint ofachieving excellent productivity of the powder, freeze-grinding ispreferred.

In polyamide resin (A1) in polyamide resin composition B of the presentinvention, another polyamide resin can also be used in such an amountthat the properties of the resultant molded article are not sacrificed.

Examples of other polyamide resins include polycaprolactam (polyamide6), polyundecanelactam (polyamide 11), polydodecanelactam (polyamide12), polyethyleneadipamide (polyamide 26), polytetramethyleneadipamide(polyamide 46), polyhexamethyleneadipamide (polyamide 66),polyhexamethyleneazelamide (polyamide 69), polyhexamethylenesebacamide(polyamide 610), polyhexamethyleneundecamide (polyamide 611),polyhexamethylenedodecamide (polyamide 612),polyhexamethyleneterephthalamide (polyamide 6T),polyhexamethyleneisophthalamide (polyamide 61),polyhexamethylenehexahydroterephthalamide (polyamide 6T(H)),polynonamethyleneadipamide (polyamide 96), polynonamethyleneazelamide(polyamide 99), polynonamethylenesebacamide (polyamide 910),polynonamethylenedodecamide (polyamide 912),polynonamethyleneterephthalamide (polyamide 9T),polytrimethylhexamethyleneterephthalamide (polyamide TMHT),polynonamethylenehexahydroterephthalamide (polyamide 9T(H)),polynonamethylenenaphthalamide (polyamide 9N),polydecamethyleneadipamide (polyamide 106), polydecamethyleneazelamide(polyamide 109), polydecamethylenedecamide (polyamide 1010),polydecamethylenedodecamide (polyamide 1012),polydecamethyleneterephthalamide (polyamide 10T),polydecamethylenehexahydroterephthalamide (polyamide 10T(H)),polydecamethylenenaphthalamide (polyamide 10N),polydodecamethyleneadipamide (polyamide 126),polydodecamethyleneazelamide (polyamide 129),polydodecamethylenesebacamide (polyamide 1210),polydodecamethylenedodecamide (polyamide 1212),polydodecamethyleneterephthalamide (polyamide 12T),polydodecamethylenehexahydroterephthalamide (polyamide 12T(H)),polydodecamethylenenaphthalamide (polyamide 12N),polymetaxylyleneadipamide (polyamide MXD6), polymetaxylylenesuberamide(polyamide MXD8), polymetaxylyleneazelamide (polyamide MXD9),polymetaxylylenesebacamide (polyamide MXD10), polymetaxylylenedodecamide(polyamide MXD12), polymetaxylyleneterephthalamide (polyamide MXDT),polymetaxylyleneisophthalamide (polyamide MXDI),polymetaxylylenenaphthalamide (polyamide MXDN),polybis(4-aminocyclohexyl)methanedodecamide (polyamide PACM12),polybis(4-aminocyclohexyl)methaneterephthalamide (polyamide PACMT),polybis(4-aminocyclohexyl)methaneisophthalamide (polyamide PACMI),polybis(3-methyl-4-aminocyclohexyl)methanedodecamide (polyamidedimethylPACM12), polyisophoroneadipamide (polyamide IPD6),polyisophoroneterephthalamide (polyamide IPDT), and polyamide copolymersthereof. These can be used individually or in combination. Of these,preferred are polyamide 6, polyamide 12, polyamide 66, polyamide 6/66copolymer (which indicates a copolymer of polyamide 6 and polyamide 66;hereinafter, a copolymer is indicated according to the same method),polyamide 6/12 copolymer, and polyamide 6/66/12 copolymer, and morepreferred are polyamide 6, polyamide 66, polyamide 6/66 copolymer, andpolyamide 6/12 copolymer.

In polyamide resin (A1) in polyamide resin composition B of the presentinvention, various additives and modifiers generally incorporated to aresin can be added in such an amount that the properties of theresultant molded article are not sacrificed. For example, a heatstabilizer, an ultraviolet light absorber, a light stabilizer, anantioxidant, an antistatic agent, a lubricant, an anti-blocking agent, afiller, a tackifier, a sealing property improving agent, an anti-foggingagent, a crystal nucleating agent, a release agent, a plasticizer, acrosslinking agent, a foaming agent, a coloring agent (e.g., a pigmentor a dye), and the like can be added during or after the polymerizationof the resin.

[At least one member selected from the group consisting of metal oxide(B1), nitrogen compound (B2), and silicon compound (B3)]

With respect to the average particle size of the at least one memberselected from the group consisting of metal oxide (B1), nitrogencompound (B2), and silicon compound (B3) used in polyamide resincomposition B of the present invention, there is no particularlimitation, but, from the viewpoint of achieving excellent physicalproperties including impact resistance, the average particle size isespecially preferably 0.1 to 200 μm, more preferably 1 to 150 μm,further preferably 5 to 100 μm. With respect to the form of theparticles, there is no particular limitation, but, from the viewpoint ofachieving excellent productivity and excellent moldability, preferred isa particulate form, particularly a round particulate form having a smallspecific surface area.

With respect to the specific surface area of the at least one memberselected from the group consisting of metal oxide (B1), nitrogencompound (B2), and silicon compound (B3), there is no particularlimitation, but the specific surface area is preferably 5 m²/g or less,more preferably 1 m²/g or less.

With respect to the purity of the at least one member selected from thegroup consisting of metal oxide (B1), nitrogen compound (B2), andsilicon compound (B3), there is no particular limitation, but, from theviewpoint of obtaining excellent electrical insulating properties andexcellent thermal conduction properties, the purity is preferably 70% bymass or more, more preferably 80% by mass or more, further preferably90% by mass or more, especially preferably 95% by mass or more.

With respect to the apparent specific gravity of the at least one memberselected from the group consisting of metal oxide (B1), nitrogencompound (B2), and silicon compound (B3), there is no particularlimitation, but, from the viewpoint of achieving excellent handlingproperties in the production (prevention of scattering), the apparentspecific gravity is preferably 0.1 g/cm³ or more.

With respect to the surface treatment for the at least one memberselected from the group consisting of metal oxide (B1), nitrogencompound (B2), and silicon compound (B3), there is no particularlimitation, and examples include a silane coupling agent andorganopolysiloxane.

Examples of metal oxides (B1) include aluminum oxide, magnesium oxide,beryllium oxide, and titanium oxide, and, from the viewpoint ofobtaining excellent electrical insulating properties and excellentthermal conduction properties, preferred are aluminum oxide andmagnesium oxide, and magnesium oxide is more preferred.

Examples of nitrogen compounds (B2) include boron nitride and aluminumnitride, and boron nitride is preferred.

As an example of silicon compound (B3), there can be mentioned calciumsilicate whiskers.

One type or two types or more can be used.

In polyamide resin composition B of the present invention, with respectto the at least one member selected from the group consisting of metaloxide (B1), nitrogen compound (B2), and silicon compound (B3), preferredis metal oxide (B1) from the viewpoint of the availability of the rawmaterial.

Polyamide resin composition B of the present invention comprises,relative to 100 parts by mass of polyamide resin (A1), preferably 25 to900 parts by mass, more preferably 33 to 600 parts by mass, furtherpreferably 42 to 300 parts by mass, especially preferably 100 to 250parts by mass of at least one member selected from the group consistingof metal oxide (B1), nitrogen compound (B2), and silicon compound (B3).

In polyamide resin composition B, a thermoplastic polymer other than thepolyamide, an elastomer, a filler, or reinforcing fibers can be addedlike the above-mentioned polyamide resin (A1) in such an amount that thedesired effects are not sacrificed.

In polyamide resin composition B, if necessary, a stabilizer, such as acopper compound, a coloring agent, an ultraviolet light absorber, alight stabilizer, an antioxidant, an antistatic agent, a flameretardant, a crystallization promoter, glass fibers, a plasticizer, alubricant, or the like can be further added.

With respect to the method for producing polyamide resin composition Bof the present invention, there is no particular limitation, but,generally, there can be mentioned the following method.

First, polyamide resin (A1), at least one member selected from the groupconsisting of metal oxide (B1), nitrogen compound (B2), and siliconcompound (B3), and an additive mentioned above as an arbitrary componentare provided.

Then, polyamide resin (A1), at least one member selected from the groupconsisting of metal oxide (B1), nitrogen compound (B2), and siliconcompound (B3), and an additive as an arbitrary component are mixed withone another using, e.g., a cylinder mixer. The resultant mixture ismelt-kneaded by means of a known extruder, such as a twin-screwextruder, a single-screw extruder, a multi-screw extruder, a Banburymixer, a roll mixer, or a kneader, to produce a polyamide resincomposition.

Examples of methods for molding polyamide resin composition B of thepresent invention into a molded article include injection molding,extrusion, blow molding, press molding, roll molding, foam molding,vacuum or pressure forming, and stretch forming. Of these, preferred aremethods by melt processing, such as injection molding, extrusion, blowmolding, press molding, roll molding, and foam molding. Polyamide resincomposition B of the present invention can be processed by the abovemolding method into, e.g., a molded article, a film, a sheet, or fibers.

The molded product using polyamide resin composition B of the presentinvention can be used in various types of molded articles in which amolded product of a polyamide resin composition has conventionally beenused, and a wide variety of applications, such as sheets, films, pipes,tubes, monofilaments, fibers, automobiles, computers and associateddevices, optical devices, information and communication devices,electric and electronic device parts for precision devices, civilengineering and construction products, medical products, and householdproducts. The molded product using polyamide resin composition B isespecially useful in applications of electric and electronic deviceparts, which require not only the inherent properties of the polyamideresin but also electrical insulating properties and thermal conductionproperties.

[Polyamide Resin Composition C]

The present invention can be polyamide resin composition C whichcomprises polyamide resin (A) and metal oxide particles (BB) as theproperty imparting component, wherein metal oxide particles (BB) containthose having a particle size of 70 μm or more in an amount of 10 to 50%by mass and those having a particle size of 20 μm or less in an amountof 1 to 50% by mass, based on the total mass of the metal oxideparticles, wherein metal oxide particles (BB) are contained in an amountof 70 to 85% by mass, based on the mass of the polyamide resincomposition.

Polyamide resin (A) in polyamide resin composition C of the presentinvention can be produced in the same manner as in polyamide resin (A)described above in connection with polyamide resin composition A, andthe same materials can be used and the same additives can be added.

The amount of polyamide resin (A) incorporated into polyamide resincomposition C of the present invention is preferably 15 to 30% by mass,based on the mass of polyamide resin composition C. When the amount ofpolyamide resin (A) is less than 15% by mass, the resultant compositionhas a reduced resin component and hence becomes brittle, making itdifficult to pelletize the strand. Further, the amount of the meltedcomponent (resin component) in the composition being kneaded is reducedto lower the fluidity, so that the kneading properties become poor. Onthe other hand, when the amount of polyamide resin (A) is more than 30%by mass, the amount of metal oxide particles (BB) incorporated isreduced, so that satisfactory thermal conduction properties cannot beexhibited. From the viewpoint of achieving excellent kneading propertiesand excellent thermal conduction properties, the amount of polyamideresin (A) incorporated into polyamide resin composition C is preferably14.9 to 29.9% by mass, more preferably 20 to 25% by mass.

[Metal Oxide Particles (BB)]

Examples of metal oxide particles (BB) used in polyamide resincomposition C of the present invention include particles of aluminumoxide, magnesium oxide, beryllium oxide, and titanium oxide, and, fromthe viewpoint of obtaining excellent electrical insulating propertiesand excellent thermal conduction properties, aluminum oxide and/ormagnesium oxide is preferred, and magnesium oxide is more preferred.

In polyamide resin composition C of the present invention, metal oxideparticles (BB), which are processed into a powdery form, are used, and,with respect to the average particle size of metal oxide particles (BB),there is no particular limitation, but, when the average particle sizeis less than 0.5 μm, the increased surface area may cause the particlesto absorb too large an amount of moisture in air, and, when the averageparticle size is more than 300 the mechanical strength including impactstrength is likely to lower, and magnesium oxide may be exposed throughthe surface of the molded article, causing the surface properties tobecome poor. Therefore, the average particle size of metal oxideparticles (BB) is preferably 0.5 to 300 μm, more preferably 12 to 73 μm,further preferably 30 to 60 μm.

In polyamide resin composition C of the present invention, metal oxideparticles (BB) contain those having a particle size of 70 μm or more inan amount of 10 to 50% by mass, preferably in an amount of 10 to 30% bymass from the viewpoint of achieving excellent physical propertiesincluding impact resistance, and contain those having a particle size of20 μm or less in an amount of 1 to 50% by mass, from the viewpoint ofachieving excellent stability of raw material transfer including feedingof raw materials during the kneading, more preferably in an amount of 15to 45% by mass, based on the total mass of the metal oxide particles.Further, from the viewpoint of achieving excellent physical propertiesincluding impact resistance and excellent kneading properties, the metaloxide particles preferably contain metal oxide particles having aparticle size of more than 20 to less than 70 μm in an amount of 40 to70% by mass, more preferably 40 to 52% by mass.

Further, in polyamide resin composition C of the present invention, fromthe viewpoint of achieving excellent thermal conduction properties,metal oxide particles (BB) preferably have a purity of 80% by mass ormore, more preferably 90% by mass or more, further preferably 95% bymass or more.

The amount of metal oxide particles (BB) incorporated into polyamideresin composition C of the present invention is 70 to 85% by mass, basedon the mass of polyamide resin composition C. When the amount of metaloxide particles (BB) is less than 70% by mass, the amount of the resinin the composition is increased, so that satisfactory thermal conductionproperties cannot be exhibited. When the amount of metal oxide particles(BB) is more than 85% by mass, the resultant strand has a reduced resinamount and hence becomes brittle, making it difficult to pelletize thestrand during the kneading. From the viewpoint of achieving excellentthermal conduction properties and excellent kneading properties, theamount of metal oxide particles (BB) is preferably 70 to 85% by mass,more preferably 75 to 85% by mass.

It is preferred that polyamide resin composition C of the presentinvention further comprises the above-mentioned polyhydric alcohol (D).In polyamide resin composition C of the present invention, polyhydricalcohol (D) is preferably a polyhydric alcohol having a meltingtemperature of 150 to 280° C., and examples of such polyhydric alcoholsinclude pentaerythritol, dipentaerythritol, and trimethylolethane, andthese can be used in combination. From the viewpoint of achievingexcellent kneading properties and excellent moldability, pentaerythritoland/or dipentaerythritol is preferred.

Further, the amount of polyhydric alcohol (D) incorporated intopolyamide resin composition C of the present invention is preferably 0.1to 5% by mass from the viewpoint of achieving excellent kneadingproperties and excellent moldability. From the viewpoint of surelyobtaining fluidity of the composition and suppressing the generation ofgas during the molding, the amount of polyhydric alcohol (D) is morepreferably 0.5 to 3% by mass.

With respect to the method for producing polyamide resin composition Cof the present invention, like the method for producing polyamide resincomposition A, there is no particular limitation as long as thecomposition is produced by melt-kneading, and various types of methodsconventionally known can be employed.

In polyamide resin composition C of the present invention, variousadditives and modifiers generally incorporated to a resin compositioncan be added in such an amount that the properties of the resultantmolded article are not sacrificed. For example, a heat stabilizer, anultraviolet light absorber, a light stabilizer, an antioxidant, anantistatic agent, a lubricant, an anti-blocking agent, a filler, ananti-fogging agent, a crystal nucleating agent, a release agent, aplasticizer, a crosslinking agent, a foaming agent, a coloring agent(e.g., a pigment or a dye), and the like can be added. With respect tothe method for adding the above additive, there is no particularlimitation, and, in addition to the above-mentioned methods forproducing the composition, various types of methods conventionally knowncan be employed. For example, there can be mentioned a dry blendingmethod.

A method for molding the obtained polyamide resin composition C into amolded article is the same method as described above in connection withpolyamide resin composition A.

A thermal conductivity of the molded article obtained from polyamideresin composition C of the present invention is measured in accordancewith JIS R-2616, and a difference between the maximum and minimum of thethermal conductivity, i.e., a thermal conductivity difference within themolded article is preferably 0.5 W/m˜K or less.

The molded product using polyamide resin composition C of the presentinvention is used in the same applications as described above inconnection with polyamide resin composition A.

Examples

Hereinbelow, the present invention will be described in more detail withreference to the following Examples, which should not be construed aslimiting the scope of the present invention.

Examples 1 to 4 (polyamide resin composition A of the present invention)and Comparative Examples 1 to 8

Various evaluation methods and the raw materials used are shown below.

(Raw Materials Used)

[Polyamide Resin (A)]

-   -   Polyamide resin (A-1): Polyamide 6 (P1011F, manufactured by Ube        Industries, Ltd., powder having an average particle size of 1 mm        or less, which has passed through a 12-mesh screen; relative        viscosity: 2.22; water extraction: 0.3% by mass; specific        gravity: 1.14)    -   Polyamide resin (A-2): Polyamide 6 (P1022, manufactured by Ube        Industries, Ltd., powder having an average particle size of 1 mm        or less, which has passed through a 12-mesh screen; relative        viscosity: 3.36; water extraction: 0.2% by mass; specific        gravity: 1.14)

[Flake Graphite (B)]

-   -   Graphite (B-1): Flake graphite (SP-10, manufactured by Nippon        Graphite Industries, Ltd.; average particle size: 20 μm; bulk        specific gravity: 0.2 g/cc; fixed carbon content: 99% by mass;        specific gravity: 2.23)    -   Graphite (B-2): Spherical graphite (LB-BG, manufactured by        Nippon Graphite Industries, Ltd.; average particle size: 30 μm;        bulk specific gravity: 0.6 g/cc; fixed carbon content: 99% by        mass; specific gravity: 2.23)

[Carbon Fibers (C)]

-   -   Carbon fibers (C-1): PAN carbon fibers (TR06NEB3E, manufactured        by Mitsubishi Rayon Co., Ltd.; fiber diameter: 7 μm; cut fiber        length: 10 mm; specific gravity: 1.8)

[Polyhydric Alcohol (D)]

-   -   Polyhydric alcohol (D-1): Pentaerythritol (manufactured by The        Nippon Synthetic Chemical Industry Co., Ltd.; melting        temperature: 260° C.; specific gravity: 1.4)

(Evaluation Methods)

(1) Kneading Properties

In producing a polyamide resin composition using TEX44, which is aco-rotation twin-screw extruder, manufactured by The Japan Steel Works,Ltd., and which has a diameter of 44 mmΦ and an L/D of 35, underkneading conditions such that the preset temperature was 290° C., thescrew speed was 200 rpm, and the discharge rate was 20 kg/hr, kneadingproperties were evaluated in accordance with the following criteria ◯and x.

x: The strand discharged from the kneader is brittle, and the strand iscut, so that the pelletization cannot be continuously performed for onehour or more. Alternatively, the load in kneading is as large as morethan 150 A which is the upper limit of the allowable current load of thekneader.

◯: The pelletization can be continuously performed for one hour or more,and further the load in kneading is not more than 150 A.

(2) Thermal Conduction Properties

Thermal conduction properties were measured in accordance with JISR-2616 (non-steady hot wire probe method).

The thermal conduction properties were evaluated in accordance with thefollowing criteria ⊚, ◯, Δ, and x.

x: Less than 4 W/m·K

Δ: To less than 7 W/m·K

◯: 7 To less than 10 W/m·K

⊚: 10 W/m·K or more

(3) Tensile Strength

A tensile strength was measured in accordance with ASTM D-638.

The tensile strength was evaluated in accordance with the followingcriteria ◯ and x.

◯: The tensile strength is 50 MPa or more.

x: The tensile strength is less than 50 MPa.

Example 1

Materials, which had the weights calculated from their respectivespecific gravities so that, relative to 100 parts by volume of polyamideresin (A-1)(polyamide 6 P1011F, manufactured by Ube Industries, Ltd.),the amount of graphite (B-1)(flake graphite SP-10, manufactured byNippon Graphite Industries, Ltd.) was 90 parts by volume, the amount ofcarbon fibers (C-1)(PAN carbon fibers TR06NEB3E, manufactured byMitsubishi Rayon Co., Ltd.) was 10 parts by volume, and the amount ofpolyhydric alcohol (D-1)(pentaerythritol, manufactured by The NipponSynthetic Chemical Industry Co., Ltd.) was 1 part by volume, werecharged into a cylinder mixer and mixed with one another. The resultantmixture was introduced into a kneader TEX44, manufactured by The JapanSteel Works, Ltd., and melt-kneaded at a preset temperature of 290° C.,a screw speed of 200 rpm, and a discharge rate of 20 kg/hr, and extrudedinto a strand form, and cooled in a water bath, and then pellets of apolyamide resin composition were obtained using a pelletizer. Thekneading properties were evaluated when producing the polyamide resincomposition. The obtained pellets of polyamide resin composition weresubjected to injection molding under conditions such that the cylindertemperature was 290° C., the mold temperature was 80° C., and thecooling time was 20 seconds to prepare a 150 mm×150 mm×3 mm testspecimen for measurement of a thermal conductivity and an ASTM No. 1dumbbell specimen having a thickness of 3.2 mm for measurement of atensile strength. Using the prepared specimens, thermal conductionproperties and tensile strength were evaluated. The results are shown inTable 1.

Example 2

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Example 1 except that the amount of graphite(B-1)(flake graphite SP-10, manufactured by Nippon Graphite Industries,Ltd.) was changed to 80 parts by volume, and they were evaluated. Theresults are shown in Table 1.

Example 3

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Example 1 except that the amount of graphite(B-1)(flake graphite SP-10, manufactured by Nippon Graphite Industries,Ltd.) was changed to 80 parts by volume, and that the amount of carbonfibers (C-1)(PAN carbon fibers TR06NEB3E, manufactured by MitsubishiRayon Co., Ltd.) was changed to 20 parts by volume, and they wereevaluated. The results are shown in Table 1.

Example 4

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Example 1 except that polyamide resin(A-1)(polyamide 6 P1011F, manufactured by Ube Industries, Ltd.) waschanged to polyamide resin (A-2): polyamide 6 (P1022, manufactured byUbe Industries, Ltd.), and they were evaluated. The results are shown inTable 1.

Comparative Example 1

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Example 1 except that, relative to 100 parts byvolume of polyamide resin (A-1)(polyamide 6 P1011F, manufactured by UbeIndustries, Ltd.), the amount of graphite (B-1)(flake graphite SP-10,manufactured by Nippon Graphite Industries, Ltd.) was changed to 100parts by volume and the amount of carbon fibers (C-1)(PAN carbon fibersTR06NEB3E, manufactured by Mitsubishi Rayon Co., Ltd.) was zero and theywere mixed together using a cylinder mixer, and they were evaluated. Theresults are shown in Table 1.

Comparative Example 2

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Comparative Example 1 except that the amount ofgraphite (B-1)(flake graphite SP-10, manufactured by Nippon GraphiteIndustries, Ltd.) was changed to 80 parts by volume, and they wereevaluated. The results are shown in Table 1.

Comparative Example 3

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Comparative Example 1 except that graphite(B-1)(flake graphite SP-10, manufactured by Nippon Graphite Industries,Ltd.) was changed to graphite (B-2)(spherical graphite LB-BG,manufactured by Nippon Graphite Industries, Ltd.), and they wereevaluated. The results are shown in Table 1.

Comparative Example 4

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Comparative Example 1 except that 80 parts byvolume of graphite (B-1)(flake graphite SP-10, manufactured by NipponGraphite Industries, Ltd.) was changed to 100 parts by volume of carbonfibers (C-1)(PAN carbon fibers TR06NEB3E, manufactured by MitsubishiRayon Co., Ltd.), and they were evaluated. The results are shown inTable 1.

Comparative Example 5

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Example 1 except that polyhydric alcohol(D-1)(pentaerythritol, manufactured by The Nippon Synthetic ChemicalIndustry Co., Ltd.) was not mixed, and they were evaluated. The resultsare shown in Table 1.

Comparative Example 6

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Example 1 except that the amount of graphite(B-1)(flake graphite SP-10, manufactured by Nippon Graphite Industries,Ltd.) was changed to 60 parts by volume, and that the amount of carbonfibers (C-1)(PAN carbon fibers TR06NEB3E, manufactured by MitsubishiRayon Co., Ltd.) was changed to 40 parts by volume, and they wereevaluated. The results are shown in Table 1.

Comparative Example 7

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Example 1 except that the amount of carbon fibers(B-1)(flake graphite SP-10, manufactured by Nippon Graphite Industries,Ltd.) was changed to 46 parts by volume, and the amount of carbon fibers(C-1)(PAN carbon fibers TR06NEB3E, manufactured by Mitsubishi Rayon Co.,Ltd.) was changed to 8 parts by volume, and they were evaluated. Theresults are shown in Table 1.

Comparative Example 8

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Comparative Example 1 except that the amount ofcarbon fibers (B-1)(PAN carbon fibers TR06NEB3E, manufactured byMitsubishi Rayon Co., Ltd.) was changed to 54 parts by volume, and theywere evaluated. The results are shown in Table 1.

TABLE 1 Carbon Polyhydric Thermal Polyamide resin Graphite fibersalcohol conduction (A) (B) (C) (D) properties Physical A-1 A-2 B-1 B-2C-1 D-1 Kneading Thermal properties Parts by Parts by Parts by Parts byParts by Parts by properties conductivity Tensile strength volume volumevolume volume volume volume Judgment W/m · k Judgment MPa JudgmentExample 1 100 90 10 1.0 ◯ 11.0 ⊚ 55 ◯ Example 2 100 80 10 1.0 ◯ 7.2 ◯ 58◯ Example 3 100 80 20 1.0 ◯ 8.1 ◯ 65 ◯ Example 4 100 90 10 1.0 ◯ 9.3 ◯52 ◯ Comparative 100 100 1.0 X 8.4 ◯ 40 X Example 1 Comparative 100 801.0 X 5.8 Δ 43 X Example 2 Comparative 100 100 1.0 X 3.9 X 45 X Example3 Comparative 100 100 1.0 X 2.2 X 250 ◯ Example 4 Comparative 100 90 10X 6.4 Δ 55 ◯ Example 5 Comparative 100 60 40 1.0 X 2.3 X 80 ◯ Example 6Comparative 100 46 8 1.0 ◯ 2.4 X 62 ◯ Example 7 Comparative 100 54 1.0 ◯2.5 X 55 ◯ Example 8

Examples 5 and 6 (Polyamide Resin Composition B of the PresentInvention) and Comparative Examples 9 and 10

(Evaluation Methods)

(1) Relative Viscosity

A relative viscosity was measured at 25° C. using an Ostwald viscometerwith respect to a solution using 96% by mass sulfuric acid as a solventand having a polyamide resin concentration of 1.0 g/dl.

(2) Melting Temperature (Tm)

A melting temperature (Tm) was measured using PYRIS Diamond DSC,manufactured by PerkinElmer Co., Ltd., in a nitrogen gas atmosphere. Theendothermic peak temperature obtained in the measurement was taken as amelting temperature.

(3) Electrical Insulating Properties

Electrical insulating properties were measured in accordance with ASTMD-257.

(4) Thermal Conduction Properties

Thermal conduction properties were measured in accordance with JISR-2616 (non-steady hot wire probe method).

(5) Tensile Strength

A tensile strength was measured in accordance with ASTM D-638.

(Raw Materials Used)

[Polyamide Resin (A1)]

-   -   Polyamide resin (A1-1): Polyamide 92

28.18 kg (139.3 mol) of dibutyl oxalate was charged into a pressurevessel having an internal volume of 150 litters and having a stirrer, athermometer, a torque meter, a pressure gauge, a raw material inletdirectly connected to a diaphragm pump, a nitrogen gas feed inlet, avent port, a pressure regulator, and a polymer withdrawal outlet, andfurther the inside of the pressure vessel was pressurized with nitrogengas having a purity of 99.9999% to 0.5 MPa, and then nitrogen gas wasreleased until the pressure became atmospheric pressure, and thisoperation was repeated 5 times to purge the vessel with nitrogen, andthen the temperature in the system was increased under a pressure whilestirring. The temperature of dibutyl oxalate was increased to 100° C.over about 30 minutes, and then a mixture of 18.74 kg (118.4 mol) of1,9-nonamethylenediamine and 3.31 kg (20.9 mol) of2-methyl-1,8-octanediamine(1,9-nonamethylenediamine:2-methyl-1,8-octanediaminemolar ratio is 85:15) was fed to the reaction vessel at a flow rate of1.49 litter/minute using the diaphragm pump over about 17 minutes andthe temperature was increased simultaneously with the feeding.

Immediately after the feeding, the internal pressure of the pressurevessel was increased to 0.35 MPa due to butanol formed by a condensationpolymerization reaction, and the temperature of the condensationpolymerization product was increased to about 170° C. Then, thetemperature was increased to 235° C. over one hour. During thetemperature increase, the internal pressure was adjusted to 0.5 MPawhile withdrawing the formed butanol from the vent port. Immediatelyafter the temperature of the condensation polymerization product reached235° C., butanol was withdrawn from the vent port over about 20 minutesso that the internal pressure became 0.11 MPa (atmospheric pressure). Ata point in time when the internal pressure became atmospheric pressure,the temperature increase was started while flowing nitrogen gas at 1.5litter/minute, and the temperature of the condensation polymerizationproduct was increased to 260° C. over about one hour, and a reaction wasconducted at 260° C. for 4.5 hours. Then, stirring was stopped and theinside of the system was pressurized with nitrogen to 1 MPa and allowedto stand for about 10 minutes, and then vented until the internalpressure became 0.5 MPa, and the resultant condensation polymerizationproduct was withdrawn in a strand form from the withdrawal outlet at thelower portion of the pressure vessel. The polymerization product in astrand form was immediately cooled with water, and the cooled resin in astrand form was pelletized by means of a pelletizer, obtaining polyamideresin (A1-1)(polyamide 92) in which the amount of the oxalic acid unitsis 100 mol %, based on the total mole of the dicarboxylic acid units.The obtained pellets were frozen with liquid nitrogen, and ground usinga pin mill, and then a powder having an average particle size of 1 mm orless, which had passed through a 16-mesh screen, was obtained. Theobtained polyamide resin (A1-1) had a relative viscosity of 2.76 and amelting temperature of 230° C.

-   -   Polyamide resin (A-1): Powdery polyamide 6 (P1011F, manufactured        by Ube Industries, Ltd.; relative viscosity: 2.22)

[At Least One Member Selected from the Group Consisting of Metal Oxide(B1), Nitrogen Compound (B2), and Silicon Compound (B3)]

-   -   Metal oxide (B1)    -   Metal oxide (B1-1): Particulate magnesium oxide (RF-50-SC,        manufactured by Ube Material Industries, Ltd.; average particle        size: 63 μm; purity: 98% by weight; apparent specific gravity:        1.5 g/cm³; specific surface area: 0.1 m²/g)

Example 5

100 Parts by mass of polyamide resin (A1-1)(polyamide 92) and 213 partsby mass of metal oxide (B1-1)(magnesium oxide, manufactured by UbeMaterial Industries, Ltd.) were mixed with each other by means of acylinder mixer. The resultant mixture was melt-kneaded at a presettemperature of 280° C. using a twin-screw extruder having a cylinderdiameter of 44 mm and an L/D of 35, and extruded into a strand form, andcooled in a water bath, and then pellets of a polyamide resincomposition were obtained using a pelletizer. The obtained polyamideresin composition was subjected to injection molding under conditionssuch that the cylinder temperature was 290° C., the mold temperature was80° C., and the cooling time was 20 seconds to prepare a 150 mm×150 mm×3mm test specimen for measurement of a thermal conductivity and a volumeresistivity and an ASTM No. 1 dumbbell specimen having a thickness of3.2 mm for measurement of a tensile strength. The obtained specimenswere subjected to treatment in a thermostatic chamber under conditionsat a temperature of 85° C. and at a relative humidity of 85% RH for 72hours, and a thermal conductivity, a volume resistivity, and a tensilestrength were measured with respect to the above-treated specimens andthe untreated specimens. The results of the evaluation are shown inTable 2.

Example 6

Substantially the same procedure as in Example 5 was conducted exceptthat the amount of metal oxide (B1-1)(magnesium oxide, manufactured byUbe Material Industries, Ltd.) was changed to 133 parts by mass. Theresults of the evaluation are shown in Table 2.

Comparative Example 9

Substantially the same procedure as in Example 5 was conducted exceptthat polyamide resin (A1-1)(polyamide 92) was changed to polyamide resin(A-1)(polyamide 6, manufactured by Ube Industries, Ltd.). The results ofthe evaluation are shown in Table 2.

Comparative Example 10

Substantially the same procedure as in Example 6 was conducted exceptthat polyamide resin (A1-1)(polyamide 92) was changed to polyamide resin(A-1)(polyamide 6, manufactured by Ube Industries, Ltd.). The results ofthe evaluation are shown in Table 2.

TABLE 2 Example Example Comparative Comparative 5 6 Example 9 Example 10Polyamide resin (A1) (A1-1) (A1-1) (A-1) (A-1) Parts by mass 100 100 100100 At least one member selected from the group consisting of metaloxide (B1), nitrogen compound (B2), and silicon compound (B3) Metaloxide (B1) (B1-1) (B1-1) (B1-1) (B1-1) Parts by mass 213 133 213 133Thermal conductivity Before treatment 1.17 0.85 1.23 0.89 [W/mK] Aftertreatment 1.15 0.88 1.27 0.97 Volume resistivity Before treatment 6.1 ×10¹⁵ 1.4 × 10¹⁶ 4.5 × 10¹⁴ 1.2 × 10¹⁵ [Ω cm] After treatment 5.0 × 10¹³3.0 × 10¹⁴ 1.2 × 10¹¹ 7.2 × 10¹⁰ Tensile strength Before treatment 70 7265 67 [MPa] After treatment 66 68 31 31

In Examples 5 and 6, which correspond to polyamide resin composition Bof the present invention, as can be clearly seen from Table 2, thelowering of the volume resistivity indicating electrical insulatingproperties and the tensile strength indicating mechanical strength dueto the high-temperature and high-humidity treatment is suppressed, andthe polyamide resin composition can exhibit excellent electricalinsulating properties and thermal conduction properties as well asmechanical strength even under high-temperature and high-humidityconditions, and exhibits especially excellent electrical insulatingproperties after a high-temperature and high-humidity treatment, andhence can be preferably used as an electrical insulating material in anelectrical insulating part.

Examples 7 to 9 (Polyamide Resin Composition C) and Comparative Examples11 to 14

(Raw Materials Used)

[Polyamide Resin (A)]

-   -   Polyamide resin (A-1): Polyamide 6 (P1011F, manufactured by Ube        Industries, Ltd., powder having an average particle size of 1 mm        or less, which has passed through a 12-mesh screen; relative        viscosity: 2.22; water extraction: 0.3% by mass; specific        gravity: 1.14)

[Metal Oxide Particles (BB)]

-   -   Magnesium oxide (BB-1): Magnesium oxide (RF-70C-SC, manufactured        by Ube Material Industries, Ltd.; average particle size: 7 μm;        purity: 99%)    -   Magnesium oxide (BB-2): Magnesium oxide (RF-50-SC, manufactured        by Ube Material Industries, Ltd.; average particle size: 53 μm;        purity: 98%)    -   Magnesium oxide (BB-3): Magnesium oxide (RF-10C-SC, manufactured        by Ube Material Industries, Ltd.; average particle size: 72 μm;        purity: 99%)

[Polyhydric Alcohol (D)]

-   -   Pentaerythritol (D-1)(manufactured by The Nippon Synthetic        Chemical Industry Co., Ltd.; melting temperature: 260° C.;        specific gravity: 1.4)        (Evaluation Methods)        (1) Kneading Properties

Kneading properties were tested and evaluated in the same manner as inpolyamide resin composition A.

(2) Thermal Conduction Properties

Thermal conduction properties were measured in accordance with JISR-2616 (non-steady hot wire probe method).

A test piece of 150 mm×150 mm×3 mmt was used, and measurement was madewith respect to three locations. The location of measurement near thegate shown in FIG. 1 was indicated by character A, and the middleportion was indicated by character B, and the end portion was indicatedby character C.

The thermal conductivity difference was obtained as a difference betweenthe maximum and minimum of the thermal conductivities measured in thethree locations.

Example 7

Polyamide resin (A-1) P1011F, manufactured by Ube Industries, Ltd., inan amount of 23.2% by mass, magnesium oxide (BB-1) RF-70C-SC,manufactured by Ube Material Industries, Ltd., in an amount of 7.6% bymass, magnesium oxide (BB-2) RF-50-SC, manufactured by Ube MaterialIndustries, Ltd., in an amount of 37.9% by mass, magnesium oxide (BB-3)RF-10C-SC, manufactured by Ube Material Industries, Ltd., in an amountof 30.3% by mass, and pentaerythritol (D-1) in an amount of 1.0% by masswere mixed together.

With respect to the particle size of magnesium oxide, particle sizedistributions of magnesium oxide (BB-1), magnesium oxide (BB-2), andmagnesium oxide (BB-3) were measured by a laser diffraction scatteringmethod in accordance with JIS R 1629, and, from the results of theparticle size distributions, the amounts of the magnesium oxide having aparticle size of 20 μm or less and the magnesium oxide having a particlesize of 70 μm or more, based on the total mass of the magnesium oxide,were determined.

The magnesium oxide incorporated had an average particle size of 37 μm,and the amount of the magnesium oxide having a particle size of 70 μm ormore was 15% by mass and the amount of the magnesium oxide having aparticle size of 20 μm or less was 41% by mass. (The amount of themagnesium oxide having a particle size 2 times or more the averageparticle size was 11% by mass, and the amount of the magnesium oxidehaving a particle size half or less of the average particle size was 41%by mass.)

These were charged into a cylinder mixer and mixed with one another, andthe resultant mixture was introduced into a kneader TEX44, manufacturedby The Japan Steel Works, Ltd., and melt-kneaded at a preset temperatureof 290° C., a screw speed of 200 rpm, and a discharge rate of 20 Kg/hr,and kneading properties were evaluated during the melt-kneading. Theobtained pellets of polyamide resin composition were subjected toinjection molding under conditions such that the cylinder temperaturewas 290° C., the mold temperature was 80° C., and the cooling time was20 seconds to prepare a 150 mm×150 mm×3 mm test specimen for measurementof a thermal conductivity. Using the prepared specimen, thermalconduction properties were evaluated with respect to measurementlocations A, B, and C. The results are shown in Table 3.

Example 8

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Example 7 except that the amount of magnesiumoxide (BB-1) RF-70C-SC, manufactured by Ube Material Industries, Ltd.,was changed to 30.3% by mass, that the amount of magnesium oxide (BB-2)RF-50-SC, manufactured by Ube Material Industries, Ltd., was 37.9% bymass, and that the amount of magnesium oxide (BB-3) RF-10C-SC,manufactured by Ube Material Industries, Ltd., was changed to 7.6% bymass, and they were evaluated. The results are shown in Table 3.

The magnesium oxide incorporated has an average particle size of 52 μm,and the amount of the magnesium oxide having a particle size of 70 μm ormore is 30% by mass and the amount of the magnesium oxide having aparticle size of 20 μm or less is 21% by mass, based on the total massof the magnesium oxide incorporated. (The amount of the magnesium oxidehaving a particle size 2 times or more the average particle size is 15%by mass, and the amount of the magnesium oxide having a particle sizehalf or less of the average particle size is 24% by mass.)

Example 9

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Example 7 except that the amount of magnesiumoxide (BB-1) RF-70C-SC, manufactured by Ube Material Industries, Ltd.,was changed to 15.2% by mass, that the amount of magnesium oxide (BB-2)RF-50-SC, manufactured by Ube Material Industries, Ltd., was changed to45.5% by mass, and that the amount of magnesium oxide (BB-3) RF-10C-SC,manufactured by Ube Material Industries, Ltd., was changed to 15.2% bymass, and they were evaluated. The results are shown in Table 3.

The magnesium oxide incorporated has an average particle size of 48 μm,and the amount of the magnesium oxide having a particle size of 70 μm ormore is 22% by mass and the amount of the magnesium oxide having aparticle size of 20 or less is 25% by mass, based on the total mass ofthe magnesium oxide mixed. (The amount of the magnesium oxide having aparticle size 2 times or more the average particle size is 10% by mass,and the amount of the magnesium oxide having a particle size half orless of the average particle size is 26% by mass.)

Comparative Example 11

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Example 7 except that polyamide resin (A-1)P1011F, manufactured by Ube Industries, Ltd., in an amount of 23.2%,magnesium oxide (BB-2) RF-50-SC, manufactured by Ube MaterialIndustries, Ltd., in an amount of 75.9% by mass, and pentaerythritol(D-1) in an amount of 1.0% by mass were mixed together, and they wereevaluated. The results are shown in Table 3.

The magnesium oxide mixed has an average particle size of 52 μm, and theamount of the magnesium oxide having a particle size of 70 μm or more is20% by mass and the amount of the magnesium oxide having a particle sizeof 20 μm or less is 0.0% by mass, based on the total mass of themagnesium oxide mixed. (The amount of the magnesium oxide having aparticle size 2 times or more the average particle size is 2% by mass,and the amount of the magnesium oxide having a particle size half orless of the average particle size is 1% by mass.)

Comparative Example 12

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Example 7 except that polyamide resin (A-1)P1011F, manufactured by Ube Industries, Ltd., in an amount of 23.2%,magnesium oxide (BB-2) RF-50-SC, manufactured by Ube MaterialIndustries, Ltd., in an amount of 30.3% by mass, magnesium oxide (BB-3)RF-10C-SC, manufactured by Ube Material Industries, Ltd., in an amountof 45.5% by mass, and pentaerythritol (D-1) in an amount of 1.0% by masswere mixed together, and they were evaluated. The results are shown inTable 3.

The magnesium oxide mixed has an average particle size of 11 μm, and theamount of the magnesium oxide having a particle size of 70 μm or more is8% by mass and the amount of the magnesium oxide having a particle sizeof 20 μm or less is 56% by mass, based on the total mass of themagnesium oxide mixed. (The amount of the magnesium oxide having aparticle size 2 times or more the average particle size is 42% by mass,and the amount of the magnesium oxide having a particle size half orless of the average particle size is 25% by mass.)

Comparative Example 13

Pellets of a polyamide resin composition were produced in substantiallythe same manner as in Example 7 except that the amount of polyamideresin (A-1) P1011F, manufactured by Ube Industries, Ltd., was changed to24.2%, that the amount of magnesium oxide (BB-1) RF-70-SC, manufacturedby Ube Material Industries, Ltd., was changed to 30.3% by mass, that theamount of magnesium oxide (BB-2) RF-50-SC, manufactured by Ube MaterialIndustries, Ltd., was 37.9% by mass, and that the amount of magnesiumoxide (BB-3) RF-10C-SC, manufactured by Ube Material Industries, Ltd.,was changed to 7.6% by mass, and they were evaluated. The results areshown in Table 3.

The magnesium oxide mixed has an average particle size of 52 μm, and theamount of the magnesium oxide having a particle size of 70 μm or more is30.0% by mass and the amount of the magnesium oxide having a particlesize of 20 μm or less is 21.0% by mass, based on the total mass of themagnesium oxide mixed. (The amount of the magnesium oxide having aparticle size 2 times or more the average particle size is 15% by mass,and the amount of the magnesium oxide having a particle size half orless of the average particle size is 24% by mass.)

Comparative Example 14

Substantially the same procedure for production as in Example 7 wasconducted except that the amount of magnesium oxide (BB-1) RF-70-SC,manufactured by Ube Material Industries, Ltd., was changed to 75.9% bymass, and that the amounts of magnesium oxide (BB-2) RF-50-SC,manufactured by Ube Material Industries, Ltd., and magnesium oxide(BB-3) RF-10C-SC, manufactured by Ube Material Industries, Ltd., werechanged to 0% by mass. However, the mixture could not be kneaded undergood conditions, making it impossible to obtain pellets of a polyamideresin composition.

The magnesium oxide mixed has an average particle size of 74 μm, and theamount of the magnesium oxide having a particle size of 70 μm or more is52.0% by mass and the amount of the magnesium oxide having a particlesize of 20 μm or less is 30.0% by mass, based on the total mass of themagnesium oxide mixed. (The amount of the magnesium oxide having aparticle size 2 times or more the average particle size is 16% by mass,and the amount of the magnesium oxide having a particle size half orless of the average particle size is 37% by mass.)

TABLE 3 Comparative Comparative Comparative Comparative Example 7Example 8 Example 9 Example 11 Example 12 Example 13 Example 14Polyamide resin (A-1) Mass % 23.2 23.2 23.2 23.2 23.2 24.2 23.2 (A)Metal oxide (BB) (BB-1) RF-70C-SC Mass % 7.6 30.3 15.2 0.0 0.0 30.3 75.9(BB-2) RF-50-SC Mass % 37.9 37.9 45.5 75.9 30.3 37.9 0.0 (BB-3)RF-10C-SC Mass % 30.3 7.6 15.2 0.0 45.5 7.6 0.0 (BB-1, BB-2, BB-3) Mass% 75.9 75.9 75.9 75.9 75.9 75.9 75.9 Total Based on 70 μm or more Mass %15 30 22 20 8 30 52 total mass of More than 20 to less than Mass % 45 4853 80 36 48 18 metal oxide 70 μm 20 μm or less Mass % 41 21 25 0 56 2130 Polyhydric (D-1) Mass % 1.0 1.0 1.0 1.0 1.0 0.0 1.0 alcohol (D)Thermal Measurement location A W/m · k 2.2 2.0 2.0 2.0 2.1 1.9 Pelletsconductivity Measurement location B W/m · k 2.0 2.0 1.8 1.7 1.6 1.7cannot be Measurement location C W/m · k 1.9 1.9 1.8 1.3 1.4 1.1obtained. Thermal conductivity W/m · k 0.3 0.1 0.3 0.7 0.7 0.8difference Kneading properties Judgment ◯ ◯ ◯ ◯ X X X

INDUSTRIAL APPLICABILITY

In the present invention, there can be provided a polyamide resincomposition which is advantageous in that a molded article havingexcellent mechanical properties or electrical insulating properties andexcellent thermal conduction properties can be obtained. Therefore, themolded article can be used in various types of molded articles in whicha molded product of a polyamide resin composition has conventionallybeen used, and a wide variety of applications, such as sheets, films,pipes, tubes, monofilaments, fibers, automobiles, computers andassociated devices, optical devices, information and communicationdevices, electric and electronic device parts for precision devices,civil engineering and construction products, medical products, andhousehold products. The molded article is especially useful inapplications of electric and electronic device parts, which require notonly the inherent properties of the polyamide resin but also thermalconduction properties.

The invention claimed is:
 1. A polyamide resin composition comprising apolyamide resin (A) and a property imparting component, the compositionbeing: a polyamide resin composition which consists essentially of thepolyamide resin (A), metal oxide particles (BB) as the propertyimparting component, and a polyhydric alcohol (D), wherein the metaloxide particles (BB) consist of magnesium oxides and contain a firstsource providing a particle size of 70 μm or more in an amount of 10 to50% by mass, a second source providing a particle size of more than 20to less than 70 μm in an amount of 40 to 70% by mass and a third sourceproviding a particle size of 20 μm or less in an amount of 1 to 50% bymass, based on the total mass of the metal oxide particles, wherein themetal oxide particles (BB) are contained in an amount of 70 to 85% bymass, based on the mass of the polyamide resin composition, and whereinthe polyhydric alcohol (D) is contained in an amount of 0.1 to 5% bymass, based on the mass of the polyamide resin composition.
 2. A moldedarticle comprising the polyamide resin composition according to claim 1.